1. Technical Field
Modes of the present invention relate to a semiconductor photocathode that emits electrons in response to incident light and a method for manufacturing the same.
2. Related Background Art
A conventionally known photocathode with a CsTe layer or a CsI layer can be used for detection of far-ultraviolet rays but is comparatively low in quantum efficiency and has strong wavelength dependence. In contrast, a photocathode using a compound semiconductor has potential for an improvement in these disadvantages.
Recent semiconductor photocathodes are described in Patent Document 1 and Patent Document 2. In Patent Document 1, a GaN layer is grown on a sapphire substrate to obtain a GaN layer of high quality. The GaN layer can be grown on a c-plane of the sapphire substrate. In both semiconductor photocathodes, a transparent substrate and a GaN layer are used and although both are capable of emitting electrons in response to incident light, sensitivities (quantum efficiencies) thereof are not sufficient. In the industrial field, demands for high precision detection of ultraviolet rays and especially detection of near-ultraviolet rays are increasing and an applicable semiconductor photocathode is being anticipated.
Near-ultraviolet rays are used in corona discharge observations, flame tests, biological agent tests, UV-LIDAR (laser imaging detection and ranging), UV Raman test apparatuses, semiconductor quality inspections, etc., and elucidation of new physical phenomena and improvements in various products can be anticipated if a highly sensitive compound semiconductor photocathode can be realized.
The above Patent Documents are as follows:    Patent Document 1: Japanese Patent No. 3623068    Patent Document 2: Japanese Patent Application Laid-Open No. 2007-165478